1. Field of the Invention
This invention relates to a disc cartridge rotatably housing therein a disc-shaped recording medium for recording information signals.
2. Description of the Related Art
Such a disc cartridge has been proposed which has a large-sized disc with a diameter of 30 cm housed therein for achieving a higher recording capacity for the recording information signals. This disc cartridge is used under hostile using conditions in which it is automatically loaded on a recording/reproducing apparatus using an automatic loading device from a housing section housing plural disc cartridges. To this end, the disc cartridge has mounted therein a disc supporting member constituted by a resilient material for being thereby protected against shock during loading or transport.
Referring to FIG. 1, a conventional disc cartridge 201 is made up of a main cartridge body portion 203, for rotatably housing an optical disc 202, and a shutter member 204 slidably mounted on this main cartridge body portion 203.
The main cartridge body portion 203 is made up of an upper cartridge half 205 and a lower cartridge half 206 abutted to each other and coupled to each other by plural set screws 207. The upper and lower cartridge halves 205, 206 are each substantially in the shape of a saucer of shallow depth so that the main cartridge body portion 203 is in the shape of a planar box. The facing inner sides of the upper and lower cartridge halves 205, 206 delimit an arcuately-shaped disc housing wall section 208 in meeting with the outer rim of the optical disc 202 for constituting a disc housing section 209.
In view of possible thermal expansion and dimensional accuracy of the optical disc 202 and the upper and lower cartridge halves 205, 206, the disc housing section 209 is formed to be larger than the outer diameter of the optical disc 202 for preventing the risk that the disc housing section be smaller than the disc diameter or preventing the optical disc 202 from being contacted with the disc housing wall section 208 during disc rotation.
At a mid portion of the main cartridge body portion 203 is formed a disc table entrance aperture 210 which is in effect an upper circular aperture and a lower circular aperture. In proximity to this disc table entrance aperture 210 is formed a recording/reproducing aperture 211 which is in effect an upper rectangular aperture and a lower rectangular aperture. On the disc table entrance aperture 210 is slidably mounted a shutter member 204 for sliding along the front side of the main cartridge body portion 203 for closing the recording/reproducing aperture 211.
The shutter member 204 is formed by warping a metallic plate, such as a thin stainless steel sheet, into a U-shape in cross-section, and is of a length sufficient to close the recording/reproducing aperture 211. The shutter member 204 is provided with a shutter guide member 213 fixedly mounted thereon. The shutter member 204 is secured to the shutter guide member 213 by set screws 214, while the shutter guide member 213 is engaged in a guide groove 212 formed along the front side edge of the main cartridge body portion 203.
On the shutter member 204 is rotatably mounted an arm 215a via a pinion gear 215b meshing with a rack gear 215c. The arm 215a has its other end mounted on a gear 216 rotatably mounted at a corner of the main cartridge body portion 203. The gear 216 is engaged with an engagement portion 217 provided on a lateral side edge adjacent to the lateral side edge of the main cartridge body portion 203 provided with the guide groove 212.
In the non-use state, the above-described shutter mechanism locks the recording/reproducing aperture 211 in the close state, with the the shutter guide member 213 being then urged by a spring 218 in the direction shown by arrow A.
When the disc cartridge 201 is loaded on the recording/reproducing apparatus, the shutter guide member 213 is moved in a direction indicated by arrow B by an opening member configured for opening the shutter guide member 213 provided on the recording/reproducing apparatus. Thus, the shutter guide member 213 is moved in a direction indicated by arrow B against the force of the spring 218, at the same time as the engagement portion 217 is slid via arm 215a and gear 216 in a direction indicated by arrow C for unlocking the shutter mechanism for opening the recording/reproducing aperture 217.
The optical disc 202, rotatably housed within the above-described main cartridge body portion 203, is made up of an inner rim side non-recording area 202b, formed with a center aperture 202a, an information signal recording area 202c formed radially outwardly of the non-recording area 202b and an outer rim side non-recording area 202d formed radially outwardly of the information signal recording area 202c.
The above-described optical disc 202 is fitted with a hub 219 having a center aperture in which is engaged a center spindle provided on the recording/reproducing apparatus for closing the center aperture 202a. This hub 219 is made up of a ring member formed of a synthetic resin material and a magnetically attracting metal plate mounted on both ends on one surface of the ring member. The hub 219 is exposed to outside by the disc table entrance aperture 210 of the disc cartridge 201.
When loaded on the recording/reproducing apparatus, the disc cartridge 201 is loaded in position on the disc table, with the center spindle engaging in the center aperture of the hub 219 and with the optical disc 202 being magnetically chucked by a magnet for being enabled to rotate in unison with the disc table.
On the facing inner sides of the upper and lower cartridge halves 205, 206 towards the inner rim of the disc housing wall section 208 and on the outer rim of the disc table entrance aperture 210, there are arranged plural disc supporting members 220 configured for softening the shock applied to the optical disc 202 loaded on the recording/reproducing apparatus.
The disc supporting member 220a is made up of a circular shock absorbing member 221a, formed of an elastic material, and a mounting plate 222a formed by a metal plate of high toughness and which is used for mounting the shock absorbing member 221a to the upper and lower cartridge halves 205, 206, as shown in FIG. 2. The shock absorbing member 221a is insert-molded at a mid portion of the mounting plate 222a.
On the other hand, since the disc supporting member 220b is provided between the disc table entrance aperture 210 and the recording/reproducing aperture 211, a band-shaped shock absorbing member 221b is insert-molded at a mid portion of the mounting piece 222b.
The disc supporting member 220, thus constructed, is mounted at a pre-set position on facing surfaces of the upper and lower cartridge halves 205, 206 by inserting and caulking a caulking pin, not shown, in a mounting hole 223 formed at each end of the mounting piece 222.
The disc cartridge 201, constructed as described above, houses the optical disc 202 of a larger diameter 30 cm and large mass. Therefore, the risk is high that, during transport or movement of the disc cartridge 201, the optical disc 202 be contacted with the disc housing wall section 208 to cause wear to the wall section 208, with the powder debris produced by wear being apt to be deposited on the upper disc surface to damage the optical disc 202.
In particular, the present disc cartridge 201 is automatically loaded to the recording/reproducing apparatus mechanically by the automatic loading device from the disc housing unit housing plural disc cartridges for recording and/or reproducing the optical disc 202. Since the disc cartridge 201 is transported or loaded/unloaded to the continuous recording and/or reproducing apparatus at an extremely high speed, the optical disc 202 housed within the disc cartridge 201 is vibrated severely and brought into abrupt contact with the disc housing wall section 208 to cause wear to the wall section 208. In such case, the powder debris produced by wear tends to be deposited in large quantities on the upper disc surface to obstruct recording and/or reproduction of information signals.
In addition, the optical disc 202 tends have a higher weight due to increased recording capacity. Thus the force of impact produced on collision of the disc surface with the disc housing wall section 208 is increased for further accelerating the wear.
Moreover, with the optical disc 202, the disc supporting member 220 is mounted for protecting the optical disc 202 from the shock produced on loading. The shock absorbing member 221 of an elastic material, used as the disc supporting member 220, is costly and cumbersome to attach to the optical disc such that it has not been possible to improve the production efficiency of the disc cartridge 201.